Feedback cancellation in hearing aids

Feedback cancellation in hearing aids is discussed. It involves estimating the feedback signal and subtracting it from the microphone input signal. The system described updates the estimated feedback path whenever changes are detected in the feedback behavior. The normal hearing-aid processing is then interrupted, a probe signal is injected into the system, and a set of filter coefficients is adjusted to give an estimate and the feedback path. Both LMS adaptive filter and Wiener filter approaches were simulated, with the Wiener filter giving better performance at poor signal-to-noise ratios. The simulation results indicate that feedback suppression in excess of 10 dB is possible